An anti-vehicle-theft device carried on a vehicle for preventing theft of the vehicle is disclosed in patent literature 1 below.
The anti-vehicle-theft device disclosed in patent literature 1 includes a sensor for detecting a vehicular abnormality and transmitting an abnormal signal indicative of the detected abnormality to a control section. The abnormal signal transmitted to the control section is transmitted through a mobile phone communication section to a base station. The base station then informs a monitoring center via a mobile phone network. The anti-vehicle-theft device is powered by a sub-battery when a main battery for feeding an electric power to the device runs out.
As discussed above, the anti-vehicle-theft device includes the sensor, the control section, the mobile phone communication section, and the sub-battery. The sensor, the control section, the mobile phone communication section and the sub-battery are accommodated within an airtight case.
The sub-battery is replaced with a new one when a life of the sub-battery ends. To replace the sub-battery, the case has a lid detachable to allow the sub-battery to be removed from the case and the new sub-battery to be attached to the case. Between the case and the lid, a seal structure should be provided to prevent entry of moisture etc. into the case during the attachment or removal of the sub-battery.
It is necessary to limit movement of the sub-battery within the case. For instance, where the sub-battery is fixed by screws etc, unscrewing operation is required, which makes the replacement of the sub-battery troublesome. Where the sub-battery is fixed using fasteners other than the screws, such fasteners need to be prepared. Because of these fasteners, the anti-vehicle-theft device increases in number of the components, size and weight. Thus, the anti-vehicle-theft device having the built-in sub-battery needs to make the case watertight and fix the sub-battery in the case in a manner to facilitate replacement of the sub-battery without requiring increase in the number of the components.